["Star Bridge," originally published in 1955,] is not a recognized "classic" of that period. According to the reference works I consulted, it stirred no controversy, won no awards, added nothing to the reputations of its authors. Not only had I never read it before, I had not even heard of it. I mention these facts only to help the reader understand my astonishment at discovering that this obscure collaboration between Williamson and [James E.] Gunn reads more like a collaboration between Heinlein and Asimov. The concept is pure, classic science fiction: A vast empire spans the galaxy, controlled from the planet Eron which alone holds the secret to faster-than-light travel….

[What] distinguishes this book from so many other Galactic Empire novels is the physical immediacy of the images….

Williamson and Gunn understand that the grander the concept, the more the reader craves specifics. The plot concerns betrayal and salvation...